| 摘要 |
PURPOSE:To obtain a tuning device which can increase the sensitivity and the degree of selection as well as decrease the tracking error. CONSTITUTION:Voltage control type tuning circuit 1 includes the parallel resonance circuit consisting of inductor L1, capacitor C1 and variable capacity diode C2 each. And variable negative resistance element -R is connected in parallel to the parallel resonance circuit. Thus resonance angle frequency omegaO and acuteness Q are controlled by control voltage Vf and VR. The shift between input signal frequency and the resonance frequency of tuning circuit 1 is detected at phase detection circuit 2, and output VD is smoothed by omegaO control voltage generation circuit 3 featuring the smooth circuit constitution in order to obtain the DC voltage. And thus control voltage Vf can be obtained in the level according to the phase difference. On the other hand, output VD is smoothed in the same way via Q control voltage generation circuit 4 to be converted into the DC level. And this DC level is applied to negative resistance element 11 in the form of proper bias signal VR to secure the optional control for Q. |
